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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<script>
    // 是真数组
var obj = { a:'1', b:'2' ,length: 3 };
console.log(
    obj instanceof Array
);//false  假数组



var Fn = Array.from(obj)
console.log(Fn instanceof Array);//true  真数组
</script>